The photo which was taken at the Pima County Cooperative Extension shows a Trichocereus Hybrid with Styrofoam cups on top to help with the cold days and nights. Photo by James S. Wood / ÃÛèÖÖ±²¥Â
Q: I live in the ÃÛèÖÖ±²¥ Foothills area where I planted three San Pedro cactus near an outdoor wash area six years ago. During the cold months, the temperature can easily drop below freezing at least seven days each winter. Since it is getting increasingly hard to cover and uncover each 5-foot-tall San Pedro cactus, can I leave the green exterior frost protection drop cloths purchased from the Home Depot  over each San Pedro cactus from late December through mid-February without damaging these plants? What time frame do you recommend for covering and protecting outdoor San Pedro cactus from frost damage?
A:Â You can certainly leave the frost cloth on if it allows light to get through. The general time frame for frost danger in our area is between mid-November and late February. Of course this is just a guideline. During the early and late ends of this range the likelihood of frost is closer to 10 percent and it is greatest between mid-December and mid-January. I recommend covering sensitive plants when local weather authorities predict danger of frost. As I am sure you know, some winters are fairly mild and you can get away with not covering your plants and then we have colder years like 2011 and this year to keep us on our toes.
